The production lines for producing stacks of honeycomb material in recent years have used various folding apparatus designs for folding the opposite longitudinal edge portions of a web usually made of a thermoplastic material over the central portion thereof. The web to be folded is unwound from a roll of the web material and is advanced through the folding apparatus of the production line by one or more driven rollers following the folding apparatus. The driven rollers press the web against freely rotatable rollers or a heating drum. The folds are set by pressing the folded web against the surface of the heating drum. The folded web is then cooled, coated with adhesive, and either spirally wound around a rotating or stationary rack, or cut into strips. In the latter case, the strips are sequentially pushed into a stacking chamber where the strips are secured together by the adhesive coating on the strips to form an expandable stack of secured together honeycomb panel-forming strips. When the adhesive coated web is wound on a rack, the opposite sides of the wound web are severed to form two secured together stacks of honeycomb panel-forming strips.
Various different types of folding apparatus have heretofore been used to fold the longitudinal edges of the web. One such apparatus is disclosed in U.S. Pat. No. 4,450,027 to Colson where the folding apparatus folds the web progressively around the bottom margins of a series of rollers having a rectangular profile. Another apparatus for folding a web is disclosed in application Ser. No. 07/839,600, filed Feb. 21, 1992, now U.S. Pat. No. 5,334,275, where the web is folded around a shoe by a series of pairs of canted rollers.
U.S. application Ser. Nos. 07/773,843, now U.S. Pat. No. 5,308,435, and 07/870,574 disclose a unique web folding apparatus over which the present invention is an improvement. The folding apparatus disclosed in these applications comprise a single folding plate having a slot therein through which the web passes. The slot has a base portion through which the central portion of the web passes, and short reversely curved slot portions at the ends of the base portion which join upwardly extending outer end slot portions which guide the opposite longitudinal edge portions of the web toward each other. The slot width desirably should usually be narrower than twice the thickness of the web to prevent fold-over of the web within the slot. The upwardly folded web is then flattened against the heated surface of the rotating heating drum and subsequently fed to cooling, adhesive-coating, web cutting and strip-stacking apparatus as above described.
The web material used in the various production lines which manufacture honeycomb material is shipped by the web supplier in the form of large rolls of such material. The supplier splices together shorter lengths of the web material using splicing strips bridging the near abutting edges of initially separate lengths of web material. The thickening of the web and splicing strip assembly where the adjacent lengths of the web material are spliced together sometimes can cause the web and strip assembly to get jammed in the desirably narrow slot of the single folding plate. This causes breakage of the web by the feeding force applied to the web and undesired stoppage of the production line.